Acne is a common inflammatory pilosebaceous disease characterized by comedones, papules, pustules, inflamed nodules, and pus-filled cysts. The pathogenesis of acne is complex and is believed to involve an interaction between hormones, keratinization, sebum, and bacteria. Acne usually begins at puberty when the increase of androgens causes an increase in the size and activity of the sebum producing ducts. These ducts can subsequently become blocked, leading to hyperkeratinization and the formation of acne lesions.
Many topical therapeutic agents are employed in the treatment of acne. It is believed that these anti-acne agents work by preventing the blockage of the ducts, by reopening clogged ducts, by acting against infecting bacteria, and by providing a keratolytic effect. Compositions containing benzoyl peroxide are known to be effective for the treatment of acne. For example, U.S. Pat. No. 3,535,422, to Cox et al., issued Oct. 20, 1970 discloses compositions containing dispersed benzoyl peroxide in a fluid medium containing water and an organic emollient; U.S. Pat. No. 4,609,674, to Gupte, issued Sep. 2, 1986, discloses stable anhydrous compositions containing benzoyl peroxide in a C.sub.6 to C.sub.10 triglyceride; U.S. Pat. No. 4,720,353 to Bell, issued Jan. 19, 1988 discloses water-in-oil emulsion compositions containing benzoyl peroxide; and U.S. Pat. No. 4,387,107, to Klein et al., issued Jun. 7, 1983 discloses aqueous benzoyl peroxide compositions employing dioctyl sodium sulfosuccinate as a wetting agent.
Even though the use of benzoyl peroxide for the treatment of acne is well known, benzoyl peroxide has the disadvantage of being very irritating to the skin, causing symptoms such as excessive drying, scaling, swelling, burning, peeling, redness, allergic contact dermatitis, and sensitization. This irritation problem associated with benzoyl peroxide can cause a patient to discontinue or to reduce its usage, thereby sacrificing the anti-acne benefit. See, e.g., Brogden et al., Drugs 8, 417 (1974); Poole et al., Arch. Derm. 102, 400 (1972); Eaglstein, Arch. Derm., 97,527 (1968); Pace, Can. Med. Ass. J., 93, 252 (1965); Vasarinsh, Arch. Derm., 98, 183 (1968); Mysliborski et al., AFP 15, 86 (1977) Hare, Br. J. Clin. Prac;, 29, 63 (1975); Fulton, et al., Arch. Derm., 110, 83 (1974); and Wilkinson, et al., Can. Med Assn. J., 95, 28 (1966).
Many conventional benzoyl peroxide compositions also have poor physical and chemical stability, and tend to lose their anti-acne effectiveness and aesthetic qualities over relatively short periods of time.
The compositions of the present invention have good anti-acne efficacy, have low skin irritancy, and are physically and chemically stable. These compositions comprise a dispersion of benzoyl peroxide in a thickened vehicle containing water and a nonvolatile liquid emollient component wherein the weighted arithmetic mean solubility parameter of the constituents of the emollient is less than or equal to about 7. Without being limited by theory, it is believed that in selecting an emollient component with this solubility parameter requirement that the solubilization of the benzoyl peroxide into the product vehicle is minimized, thereby reducing the incidence of unwanted skin irritation and other undesired side effects due to excessive epidermal penetration. It is also believed that the emollient component provides the additional benefit of coating and soothing the skin, thereby further mitigating any potentially irritating effects from the benzoyl peroxide. Also, it is believed that the limited solubility of the benzoyl peroxide in the present compositions provides enhanced chemical and physical stability of the compositions.
It is therefore an object of the present invention to provide topical compositions for the treatment of acne.
It is another object of the present invention to provide topical compositions for the treatment of acne, which comprise benzoyl peroxide as the active ingredient, and which have good efficacy, low skin irritation, and good physical and chemical stability.
It is another object of the present invention to provide a method for treating acne in human skin.
These and other objects of this invention will become apparent in light of the following disclosure.